Question

A person pushes a desk across the horizontal floor with a constant force of $20.0N$. The desk moves at a constant $2.0m/s$. If the only other acting on the desk is the force of friction, how does the amount of frictional force compare to the amount of force the person applies?

• A. The force of friction must be greater than the force the person applies
• B. The force a friction must be less than the force the person applies
• C. The force of friction must be the same as the force the person applies
• D. The force of friction must be zero
• E. Not enough information is given to answer this question

Answer 1

Answer: (C)

The force of friction must be the same as the force the person applies

Since the desk moves with constant speed of $2m/s$, it is not acceleration.

Hence the net force acting on the desk is zero.

$⟹F+(-f)=0$

$⟹$ Force of friction=$f=F=20N$
Correct answer is option C.